1. Field of the Invention
The present invention relates generally to an optical sheet that is applicable to the screen of a display system and, more particularly, to a microlens array sheet having a black matrix and a method of manufacturing the same, in which, in order to form the black matrix that is a light blocking layer that covers regions other than light apertures, a light aperture pattern is formed through an exposure process performed toward a microlens sheet and on a light-sensitive resin layer under the microlens sheet, and the regions other than the light apertures are filled with a black pigment having a considerably low light reflective index and a considerably low transmittance.
2. Description of the Related Art
A screen used in a projection-type display system includes a microlens array sheet for spatially distributing emitted light collimated through an optical system so that the light can have a desired viewing angle, a black matrix layer for improving contrast by absorbing external light and minimizing the reflection of external light, and a light diffusion layer for diffusing the emitted light and eliminating speckles. In particular, a black matrix that is currently used to improve contrast is manufactured using methods, such as a Cr/CrOx metallization method, a resin black matrix method, a black matrix transfer method, etc.
The black matrix formation method using Cr/CrOx, which is mainly employed in a Liquid Crystal Display (LCD), uses Cr having an optical density of more than 3.5, so that it has characteristics of excellent light blocking performance and chemical resistance. However, the black matrix formation method is disadvantageous in that the process thereof is complicated and a facility cost is high, thus increasing the manufacturing cost because Cr/CrOx layers having a thickness of 0.1˜0.2 μm must be sequentially laid one on top of another and then be etched. Furthermore, since Cr has a high reflective index, an additional process for achieving a low reflective characteristic is necessary.
The resin black matrix method, using resin including a black pigment, is advantageous in that it is simple because it forms a black matrix using photolithography after applying the resin. However, it is disadvantageous in that it is difficult to perform photolithography because a large amount of black pigment is required to attain high optical density and because exposure light, such as ultraviolet light for photolithography, cannot generally penetrate a high-density material in the depth direction thereof. In order to achieve desired optical density, the amount of a black pigment must be increased and the amount of resin must be decreased, so that a patterned shape formed through a developing process becomes rough due to the relatively small proportion of the resin, thus causing degradation in the brightness and viewing angle of an optical sheet having the black matrix that is formed by the above-described method.
The black matrix formation method using a pattern transfer technique includes a method using a light-sensitive adhesion layer and a method using a photothermal conversion layer.
The method using a light-sensitive adhesion layer utilizes the characteristic of a material in which portions onto which light is radiated lose adhesiveness. This method is a method of transferring a black matrix after radiating light onto a microlens sheet having a light-sensitive adhesion layer. This method is disadvantageous in that the boundary surfaces of light apertures, which are formed by the transfer of the black matrix, are rough, so that some light passing through the light apertures is lost.
Meanwhile, the method using a photothermal conversion layer is a method of transferring a black matrix from a donor substrate having a substrate, a photothermal conversion layer and a transfer layer to an acceptor substrate on which the black matrix is to be formed. This method is disadvantageous in that the donor substrate is relatively complicated, so that the manufacturing cost thereof increases.